Thermoplastic films with visually-distinct stretched regions and methods for making the same

ABSTRACT

Thermoplastic films include intermittent stretched regions that are visually distinct from un-stretched regions. The stretched regions can be white, opaque, and non porous. The thermoplastic films with visually-distinct stretched regions can be formed into bags for use as trash can liners or food storage. Additionally, methods of stretching thermoplastic films to create non-porous, white, and opaque stretched regions include incrementally stretching a film of a thermoplastic material and a voiding agent.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.61/478,639, filed Apr. 25, 2011, which is hereby incorporated byreference in its entirety.

BACKGROUND OF THE INVENTION

1. The Field of the Invention

The present invention relates generally to thermoplastic films.Specifically, the invention relates to stretched thermoplastic filmswith visual effects created by voiding agents.

2. Background and Relevant Art

Thermoplastic films are a common component in various commercial andconsumer products. For example, grocery bags, trash bags, sacks, andpackaging materials are products that are commonly made fromthermoplastic films. Additionally, feminine hygiene products, babydiapers, adult incontinence products, and many other products includethermoplastic films to one extent or another.

Thermoplastic films have a variety of different strength parameters thatmanufacturers of products incorporating a thermoplastic film componentmay attempt to manipulate to ensure that the film is suitable for useits intended use. For example, manufacturers may attempt to increase orotherwise control the tensile strength, tear resistance, impactresistance, and breathability of a thermoplastic film. One waymanufacturers may attempt to control or change the material propertiesof a thermoplastic film is by stretching the film. Common directions ofstretching include “machine direction” and “transverse direction”stretching. As used herein, the term “machine direction” or “MD” refersto the direction along the length of the film, or in other words, thedirection of the film as the film is formed during extrusion and/orcoating. As used herein, the term “transverse direction” or “TD” refersto the direction across the film or perpendicular to the machinedirection.

Common ways of stretching film in the machine direction include machinedirection orientation (“MDO”) and incremental stretching. MDO involvesstretching the film between two pairs of smooth rollers. Commonly MDOinvolves running a film through the nips of sequential pairs of smoothrollers. The first pair of rollers rotates at a speed less than that ofthe second pair of rollers. The difference in speed of rotation of thepairs of rollers can cause the film between the pairs of rollers tostretch. The ratio of the roller speeds will roughly determine theamount that the film is stretched. For example, if the first pair ofrollers is rotating at 100 feet per minute (“fpm”) and the second pairof rollers is rotating at 500 fpm, the rollers will stretch the film toroughly five times its original length. MDO stretches the filmcontinuously in the machine direction and is often used to create anoriented film.

Incremental stretching of thermoplastic film, on the other hand,typically involves running the film between grooved or toothed rollers.The grooves or teeth on the rollers intermesh and stretch the film asthe film passes between the rollers. Incremental stretching can stretcha film in many small increments that are spaced across the film. Thedepth at which the intermeshing teeth engage can control the degree ofstretching. Often, incremental stretching of films is referred to asring rolling.

In connection with stretching a film, manufacturers may add a voidingagent to the film. Upon stretching, the voiding agent can create voidsin the film; thereby, producing a breathable film. Manufacturerscommonly use relatively large amounts of filler (50% by weight) and/orheat the film to an elevated temperature during stretching when creatingbreathable or porous films.

In addition to allowing for the modification or tailoring of thestrength and the breathability of a film, stretching of a film can alsoreduce the thickness of the film. Stretched films of reduced thicknesscan allow manufacturers to use less thermoplastic material to form aproduct of a given surface area or size. Reducing the gauge of a film;however, can make the film more transparent or translucent. Consumerscommonly associate thinner films and/or transparent films with weakness;and thus, may be dissuaded to purchase stretched films. Manufacturersmay add pigments, such as TiO₂, to add either color or opacity tothinner films. Unfortunately, additives, such as TiO₂ can be expensiveand often negatively impact the film strength properties, especially asthe additive concentration is increased. Furthermore, even pigmentedfilms commonly become less opaque upon stretching.

One common use of thermoplastic films is as bags for liners in trash orrefuse receptacles. It is often undesirable to use porous or breathablefilms in trash bags as the voids in porous films may allow odor and/orliquids to escape from the bag. Additionally, many consumers may preferopaque and non-transparent trash bags that prevent others (i.e.,neighbors) from viewing the contents in the trash bag.

Another common use of thermoplastic films is as flexible plastic bagsfor storing food items. Similar to trash bags, in some instances it maybe undesirable to use porous or breathable films in food storage bagsbecause the voids in porous films can allow air and/or germs to reachand spoil the food within food storage bag. In other instances, however,a breathable food storage bag may be desirable. For example, abreathable food storage bag may be desirable when storing fruit and/orvegetables.

Accordingly, there are a number of considerations to be made inthermoplastic films and manufacturing methods.

BRIEF SUMMARY OF THE INVENTION

Implementations of the present invention solve one or more problems inthe art with apparatus and methods for creating films withvisually-distinct stretched regions. In particular, one or moreimplementations of the present invention include incrementallystretching films formed from a thermoplastic material and a voidingagent. Upon stretching, the voiding agent can cause the stretchedregions of the film to become more opaque than un-stretched regions ofthe film. Additionally, one or more implementations of the presentinvention include methods of incrementally-stretching films to createvisually-distinct stretched regions.

For example, one implementation of a thermoplastic film can include afirst plurality of un-stretched regions. The film can also include asecond plurality of stretched regions intermittently dispersed about thefirst plurality of un-stretched regions. The stretched regions can benon-porous and more opaque than the un-stretched regions.

Additionally, one or more implementations of the present inventioninclude a thermoplastic bag that includes first and second sidewalls.The first and second sidewalls can be joined along three edges. Thethermoplastic bag can include a plurality of un-stretched regions formedin one or more of the first sidewall or the second sidewall. Theun-stretched regions can have a first average thickness. Thethermoplastic bag can also include a plurality of stretched regionsintermittently dispersed about the un-stretched regions. The stretchedregions can have a second average thickness that is smaller than thefirst average thickness. Additionally, the stretched regions can be moreopaque then un-stretched regions.

In addition to the forgoing, a method for incrementally stretching afilm to create visually distinct regions can involve providing athermoplastic film. The thermoplastic film can comprise between about 65and about 99 percent by weight of a thermoplastic material and betweenabout 1 and about 35 percent by weight of a voiding agent. The methodcan also involve cold stretching the film to create non-porous stretchedregions intermittingly dispersed among un-stretched regions. Thestretched regions can be more opaque than the un-stretched regions ofthe film.

Additional features and advantages of exemplary embodiments of thepresent invention will be set forth in the description which follows,and in part will be obvious from the description, or may be learned bythe practice of such exemplary embodiments. The features and advantagesof such embodiments may be realized and obtained by means of theinstruments and combinations particularly pointed out in the appendedclaims. These and other features will become more fully apparent fromthe following description and appended claims, or may be learned by thepractice of such exemplary embodiments as set forth hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to describe the manner in which the above-recited and otheradvantages and features of the invention can be obtained, a moreparticular description of the invention briefly described above will berendered by reference to specific embodiments thereof which areillustrated in the appended drawings. It should be noted that thefigures are not drawn to scale, and that elements of similar structureor function are generally represented by like reference numerals forillustrative purposes throughout the figures. Understanding that thesedrawings depict only typical embodiments of the invention and are nottherefore to be considered to be limiting of its scope, the inventionwill be described and explained with additional specificity and detailthrough the use of the accompanying drawings in which:

FIG. 1A illustrates a schematic diagram of a thermoplastic film beingincrementally stretched by MD intermeshing rollers in accordance withone or more implementations of the present invention;

FIG. 1B illustrates an enlarged view of a portion of the thermoplasticfilm passing through the intermeshing rollers of FIG. 1A taken along thecircle 1B of FIG. 1;

FIG. 2 illustrates a view of a thermoplastic film includingvisually-distinct stretched regions created by the intermeshing rollersof FIG. 1;

FIG. 3 illustrates a schematic diagram of a thermoplastic film beingincrementally stretched by TD intermeshing rollers in accordance withone or more implementations of the present invention;

FIG. 4 illustrates a view of a thermoplastic film includingvisually-distinct stretched regions created by the intermeshing rollersof FIG. 3;

FIG. 5 illustrates a view of a thermoplastic film includingvisually-distinct stretched regions created by the intermeshing rollersof both FIG. 1 and FIG. 3;

FIG. 6 illustrates a view of thermoplastic film includingvisually-distinct stretched regions created by diagonal directionintermeshing rollers in accordance with one or more implementations ofthe present invention;

FIG. 7 illustrates a schematic diagram of a set of intermeshing rollersused to impart strainable networks into a film in accordance with one ormore implementations of the present invention;

FIG. 8 illustrates a view of a thermoplastic film includingvisually-distinct stretched regions created by the intermeshing rollersof FIG. 7;

FIG. 9 illustrates a view of a thermoplastic film including strainablenetworks having visually-distinct stretched regions in accordance withone or more implementations of the present invention;

FIG. 10 illustrates a bag incorporating the film of FIG. 2;

FIG. 11 illustrates a bag incorporating a film having visually-distinctstretched regions in accordance with one or more implementations of thepresent invention;

FIG. 12 illustrates a bag incorporating a middle section havingvisually-distinct stretched regions in accordance with one or moreimplementations of the present invention;

FIG. 13 illustrates a bag incorporating sections of different patternsof visually-distinct stretched regions in accordance with one or moreimplementations of the present invention;

FIG. 14 illustrates another bag incorporating sections of differentpatterns of visually-distinct stretched regions in accordance with oneor more implementations of the present invention;

FIG. 15 illustrates a schematic diagram of a bag manufacturing processin accordance with one or more implementations of the present invention;

FIG. 16 illustrates a schematic diagram of another bag manufacturingprocess in accordance with one or more implementations of the presentinvention; and

FIG. 17 illustrates a schematic diagram of yet another bag manufacturingprocess in accordance with one or more implementations of the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

One or more implementations of the present invention include apparatusand methods for creating films with visually-distinct stretched regions.In particular, one or more implementations of the present inventioninclude incrementally stretching films formed from a thermoplasticmaterial and a voiding agent. Upon stretching, the voiding agent cancause the stretched regions of the film to become more opaque thanun-stretched regions of the film. Additionally, one or moreimplementations of the present invention include methods ofincrementally-stretching films to create visually-distinct stretchedregions.

Indeed, one or more implementations of the present invention can providethermoplastic films, and products made there from, withvisually-distinct stretched regions. As used herein, the term “visuallydistinct” refers to a feature that is more opaque and potentially adifferent color from another feature in a manner that is visible to thenaked eye. In one or more implementations, the visually-distinctstretched regions can be white and opaque. The opacity of thevisually-distinct stretched regions can make the stretched regionsappear thick and can connote strength to a consumer.

In addition to the foregoing, one or more implementations providestretched thermoplastic films with visually distinct regions thatconsumers can associate with improved properties created by stretchingthe film. For example, the visually distinct regions can indicate thatthose regions have undergone a transformation to impart a desirablecharacteristic to that region (e.g., increased strength or elasticity).Thus, the visually distinct regions can serve to notify a consumer thatthe thermoplastic film has been processed to improve the film.

Furthermore, different areas of a film can include different types ofstretching; and thus, different strength characteristics. The differentvisually-distinct stretched regions created by the different types ofstretching can serve to notify the consumer that the different areas orzones of the film have been tailored with different characteristics. Forexample, one or more implementations of the present invention includesusing MD ring rolling, TD ring rolling, diagonal direction (“DD”) ringrolling, and the formation of strainable networks, and combinationsthereof to create different stress-whitened patterns in a film. As usedherein, “stress-whitening” or “stress-whitened” refers to a filmbecoming more opaque and/or whiter upon stretching. In addition todifferent types of stretching, intermeshing rollers with different toothpitches and/or layouts can allow for the creation of visually-distinctstress-whitened patterns in a film. Also, the film can include one ormore pigments of a color other than white. Thus upon stretching, thewhitened stretched regions can contrast with the colored un-stretchedregions.

Additionally, consumers may associate thinner films with decreasedstrength. Indeed, such consumers may feel that they are receiving lessvalue for their money when purchasing thermoplastic film products withthinner gauges. One will appreciate in light of the disclosure hereinthat a consumer may not readily detect that one or moreincrementally-stretched films of the present invention have a reducedgauge. In particular, by imparting an alternating pattern of visuallydistinct regions, the consumer may perceive the more opaque regions asbeing thicker and/or having increased strength.

As explained in greater detail below, the use of a voiding agent tocreate visually-distinct stretched regions can allow a manufacturer touse less pigments, such as TiO₂, to color or add opacity to a film. Thereduction in pigments can lead to significant cost savings. Furthermore,pigments can become less effective as a film is stretched; thus, one ormore implementations of the implementations of the present invention canbe more effective in adding opacity to stretched films than pigmentsalone.

As alluded to previously, voiding agents are commonly added to films soas to create porous or breathable films upon stretching. One or moreimplementations include adding relatively small amounts of a voidingagent(s) and/or stretching the film under ambient or cold (non-heated)conditions to allow for the creation of stress-whitened regions withoutcreating a porous film. This differs significantly from mostconventional processes that stretch films including voiding agents. Inparticular, most conventional processes that stretch films includingvoiding agents stretch the films under heated conditions and includerelatively large amounts of the voiding agent. Stretching under ambientor cold conditions in accordance with one or more implementations canconstrain the molecules in the film so they are not as easily orientedas under heated conditions, so as to help prevent the creation of aporous film.

Film Materials

As an initial matter, in one or more implementations the films (e.g.,10-10 e of FIGS. 1A-9) can comprise a thermoplastic material and avoiding agent. In alterative implementations, the films (e.g., 10-10 cof FIGS. 1A-9) may comprise a thermoplastic material(s) that stresswhitens without a voiding agent. The thermoplastic material of the filmsof one or more implementations can include, but are not limited to,thermoplastic polyolefins, including polyethylene and copolymers thereofand polypropylene and copolymers thereof. The olefin based polymers caninclude the most common ethylene or propylene based polymers such aspolyethylene, polypropylene, and copolymers such as ethylenevinylacetate (EVA), ethylene methyl acrylate (EMA) and ethylene acrylicacid (EAA), or blends of such polyolefins.

Other examples of polymers suitable for use as films in accordance withthe present invention include elastomeric polymers. Suitable elastomericpolymers may also be biodegradable or environmentally degradable.Suitable elastomeric polymers for the film includepoly(ethylene-butene), poly(ethylene-hexene), poly(ethylene-octene),poly(ethylene-propylene), poly(styrene-butadiene-styrene),poly(styrene-isoprene-styrene), poly(styrene-ethylene-butylene-styrene),poly(ester-ether), poly(ether-amide), poly(ethylene-vinylacetate),poly(ethylene-methylacrylate), poly(ethylene-acrylic acid),poly(ethylene butylacrylate), polyurethane,poly(ethylene-propylene-diene), ethylene-propylene rubber.

In at least one implementation of the present invention, the film caninclude linear low density polyethylene. The term “linear low densitypolyethylene” (LLDPE) as used herein is defined to mean a copolymer ofethylene and a minor amount of an olefin containing 4 to 10 carbonatoms, having a density of from about 0.910 to about 0.926, and a meltindex (MI) of from about 0.5 to about 10. For example, someimplementations of the present invention can use an octene comonomer,solution phase LLDPE (MI=1.1; ρ=0.920). Additionally, otherimplementations of the present invention can use a gas phase LLDPE,which is a hexene gas phase LLDPE formulated with slip/AB (MI=1.0;ρ=0.920). One will appreciate that the present invention is not limitedto LLDPE, and can include “high density polyethylene” (HDPE), “lowdensity polyethylene” (LDPE), and “very low density polyethylene”(VLDPE). Indeed films made from any of the previously mentionedthermoplastic materials or combinations thereof can be suitable for usewith the present invention.

LLDPE will typically not stress whiten without a voiding agent. Thus,films of one or more implementations of the present invention includingLLDPE may also include a voiding agent. Furthermore, LLDPE is typicallynot a candidate material for conventional film orientations methodsbecause its relatively high crystallinity can result in a relativelysharp melting point. The relatively sharp melting point can make LLDPEdifficult to process. As such, stretching LLDPE by conventional meanswith voiding agents to create breathable films can be difficult.

Indeed, implementations of the present invention can include anyflexible or pliable thermoplastic material which may be formed or drawninto a web or film. Furthermore, the thermoplastic materials may includea single layer or multiple layers. The thermoplastic material may beopaque, transparent, translucent, or tinted. Furthermore, thethermoplastic material may be gas permeable or impermeable.

As used herein, the term “flexible” refers to materials that are capableof being flexed or bent, especially repeatedly, such that they arepliant and yieldable in response to externally applied forces.Accordingly, “flexible” is substantially opposite in meaning to theterms inflexible, rigid, or unyielding. Materials and structures thatare flexible, therefore, may be altered in shape and structure toaccommodate external forces and to conform to the shape of objectsbrought into contact with them without losing their integrity. Inaccordance with further prior art materials, web materials are providedwhich exhibit an “elastic-like” behavior in the direction of appliedstrain without the use of added traditional elastic. As used herein, theterm “elastic-like” describes the behavior of web materials which whensubjected to an applied strain, the web materials extend in thedirection of applied strain, and when the applied strain is released theweb materials return, to a degree, to their pre-strained condition.

In addition to a thermoplastic material, the films of one or moreimplementations of the present invention can also include a voidingagent. Some examples of voiding agents suitable for use in the presentinvention include calcium carbonate, magnesium carbonate, bariumcarbonate, calcium sulfate, magnesium sulfate, barium sulfate, calciumoxide, magnesium oxide, titanium oxide, zinc oxide, aluminum hydroxide,magnesium hydroxide, talc, clay, silica, alumina, mica, glass powder,starch, etc. One will appreciate in light of the disclosure herein thatthe foregoing list of voiding agents are examples of some of the voidingagents that may be suitable for use with the present invention.

Films of one or more implementations of the present invention mayinclude other voiding agents, or combinations of any of the previouslymentioned voiding agents. Indeed, in one or more implementations, thevoiding agent any be any inorganic or organic material with a relativelylower elasticity than the thermoplastic material of the film. In one ormore implementations, calcium carbonate may be particularly suitable forits whiteness, inert characteristic, low cost, and availability.

In addition to a thermoplastic material and a voiding agent, films ofone or more implementations of the present invention can also includeone or more additives. For examples, the films can include pigments,slip agents, anti-block agents, or tackifiers. The pigments can includeTiO₂, or other pigments, that can impart a color and/or opacity to thefilm.

One will appreciate in light of the disclosure herein that manufacturersmay form the films or webs to be used with the present invention using awide variety of techniques. For example, a manufacturer can formprecursor mix of the thermoplastic material, a voiding agent, and one ormore additives. The manufacturer can then form the film(s) from theprecursor mix using conventional flat or cast extrusion or coextrusionto produce monolayer, bilayer, or multilayer films. Alternatively, amanufacturer can form the films using suitable processes, such as, ablown film process to produce monolayer, bilayer, or multilayer films.If desired for a given end use, the manufacturer can orient the films bytrapped bubble, tenterframe, or other suitable process. Additionally,the manufacturer can optionally anneal the films thereafter.

In one or more implementations, the films of the present invention areblown film, or cast film. Blown film and cast film is formed byextrusion. The extruder used can be a conventional one using a die,which will provide the desired gauge. Some useful extruders aredescribed in U.S. Pat. Nos. 4,814,135; 4,857,600; 5,076,988; 5,153,382;each of which are incorporated herein by reference in their entirety.Examples of various extruders, which can be used in producing the filmsto be used with the present invention, can be a single screw typemodified with a blown film die, an air ring, and continuous take offequipment.

In a blown film process, the die can be an upright cylinder with acircular opening. Rollers can pull molten plastic upward away from thedie. An air-ring can cool the film as the film travels upwards. An airoutlet can force compressed air into the center of the extruded circularprofile, creating a bubble. The air can expand the extruded circularcross section by a multiple of the die diameter. This ratio is calledthe “blow-up ratio.” When using a blown film process, the manufacturercan collapse the film to double the plies of the film. Alternatively,the manufacturer can cut and fold the film, or cut and leave the filmunfolded.

As used herein, the term “starting gauge” or “initial gauge” refers tothe average distance between the major surfaces of a film before it isincrementally stretched. The films of one or more implementations of thepresent invention can have a starting gauge between about 0.1 mils toabout 20 mils, suitably from about 0.2 mils to about 4 mils, suitably inthe range of about 0.3 mils to about 2 mils, suitably from about 0.6mils to about 1.25 mils, suitably from about 0.9 mils to about 1.1 mils,suitably from about 0.3 mils to about 0.7 mils, and suitably from about0.4 mils and about 0.6 mils. Additionally, the starting gauge of filmsof one or more implementations of the present invention may not beuniform. Thus, the starting gauge of films of one or moreimplementations of the present invention may vary along the lengthand/or width of the film.

In one or more implementations of the present invention, theincrementally-stretched films with visually-distinct stretched regionsare non porous or non breathable. As used herein, the terms “non porous”and “non breathable” refer to a films that are liquid impermeable and atleast substantially gas/vapor impermeable. Thus, a non-porous ornon-breathable film may not allow liquids or gases to pass therethrough. Because the incrementally-stretched films withvisually-distinct stretched regions of one or more implementations arenon porous or non breathable, they may be particularly suited for use intrash liners or food storage bags. In one or more additionalimplementations, the incrementally-stretched films withvisually-distinct stretched regions may be liquid impermeable, yetgas/vapor permeable. Such incrementally-stretched films withvisually-distinct stretched regions of one or more implementations maybe particularly suited for use in food storage bags.

It should be noted that the non-porous or non-breathable films of thepresent invention can include voids. The voids can create thestress-whitened and/or opaque appearance in the stretched regions. Onewill appreciate, however, that the size, number, and/or depth of thevoids may prevent liquid from passing through the film. Furthermore, insome implementations, the size, number, and/or depth of the voids maysubstantially prevent gases and vapors from passing through the film. Instill further implementations, the size, number, and/or depth of thevoids may completely prevent gases and vapors from passing through thefilm.

The size, number, and/or depth of the voids can be controlled to ensurea non-porous film by controlling one or more of the amount of thevoiding agent in the film, the degree or amount of stretching, and thetemperature of the film upon stretching. For example, in one or moreimplementations the percent weight of the voiding agent in the film canbe suitably between about 1% and about 35%, suitably between about 1%and about 30%, suitably between about 5% and about 25%, suitably betweenabout 5% and about 20%, and suitably between about 10% and about 15%.

Additionally, one or more implementations include incrementallystretching the film under ambient or cold (non-heated) conditions.Furthermore, one or more implementations include stretching the film atratios less than about 1:3. In other words, one or more implementationsinclude stretching the film less than about 3 times its originaldimension (e.g., length, width). Suitably one or more implementationsinclude stretching the film less than about 1.5 times its originaldimension (e.g., length, width).

Referring now to the Figures, FIGS. 1A and 1B illustrate one exemplaryprocess of incrementally stretching a thermoplastic film to createvisually-distinct stretched regions in accordance with an implementationof the present invention. In particular, FIGS. 1A and 1B illustrate anMD ring rolling process that incrementally stretches a thermoplasticfilm 10 by passing the film 10 through a pair of MD intermeshing rollers12, 14. The MD ring rolling processes of the present invention canstretch the film 10 in the machine direction.

As shown by the FIGS. 1A and 1B, the first roller 12 and the secondroller 14 can each have a generally cylindrical shape. The rollers 12,14 may be made of cast and/or machined metal, such as, steel, aluminum,or any other suitable material. The rollers 12, 14 can rotate inopposite direction about parallel axes of rotation. For example, FIG. 1Aillustrates that the first roller 12 can rotate about a first axis 16 ofrotation in a counterclockwise direction 18. FIG. 1A also illustratesthat the second roller 14 can rotate about a second axis 20 of rotationin a clockwise direction 22. The axes of rotation 16, 20 can be parallelto the transverse direction and perpendicular to the machine direction.

The intermeshing rollers 12, 14 can closely resemble fine pitch spurgears. In particular, the rollers 12, 14 can include a plurality ofprotruding ridges 24, 26. The ridges 24, 26 can extend along the rollers12, 14 in a direction generally parallel to axes of rotation 16, 20.Furthermore, the ridges 24, 26 can extend generally radially outwardfrom the axes of rotation 16, 20. The tips of ridges 24, 26 can have avariety of different shapes and configurations. For example, the tips ofthe ridges 24, 26 can have a rounded shape as shown in FIG. 1B. Inalternative implementations, the tips of the ridges 24, 26 can havesharp angled corners. FIGS. 1A and 1B also illustrate that grooves 28,30 can separate adjacent ridges 24, 26.

The ridges 24 on the first roller 12 can be offset or staggered withrespect to the ridges 26 on the second roller 14. Thus, the grooves 28of the first roller 12 can receive the ridges 26 of the second roller14, as the rollers 12, 14 intermesh. Similarly, the grooves 30 of thesecond roller 14 can receive the ridges 24 of the first roller 12. Inone or more implementations, the ridges 24, 26 will not contact eachother or transmit rotational torque during an intermeshing stretchingoperation.

One will appreciate in light of the disclosure herein that theconfiguration of the ridges 24, 26 and grooves 28, 30 can preventcontact between ridges 24, 26 during intermeshing. Additionally, theconfiguration of the ridges 24, 26 and grooves 28, 30 can dictate theamount stretching a film passing through the MD intermeshing rollers 12,14 undergoes.

Referring specifically to FIG. 1B, various features of the ridges 24, 26and grooves 28, 30 are shown in greater detail. The pitch and depth ofengagement of the ridges 24, 26 can determine, at least in part, theamount of incremental stretching created by the intermeshing rollers 12,14. As shown by FIG. 1B, the pitch 32 is the distance between the tipsof two adjacent ridges on the same roller. The “depth of engagement”(DOE) 34 is the amount of overlap between ridges 24, 26 of the differentrollers 12, 14 during intermeshing. The ratio of DOE 34 to pitch 32 candetermine, at least in part, the amount of stretch imparted by a pair ofintermeshing rollers 12, 14.

As shown by FIG. 1A, the direction of travel of the film 10 through theintermeshing rollers 12, 14 is parallel to the machine direction andperpendicular to the transverse direction. As the thermoplastic film 10passes between the intermeshing rollers 12, 14, the ridges 24, 26 canincrementally stretch the film 10 in the machine direction. In someimplementations, stretching the film 10 in the machine direction canreduce the gauge of the film and increase the length of the film 10. Inother implementations, the film 10 may rebound after stretched such thatthe gauge of the film 10 is not decreased. Furthermore, in someimplementations, stretching the film 10 in the machine direction canreduce the width of the film 10. For example, as the film 10 islengthened in the machine direction, the film's length can be reduced inthe transverse direction.

In particular, as the film 10 proceeds between the intermeshing rollers12, 14, the ridges 24 of the first roller 12 can push the film 10 intothe grooves 30 of the second roller 14 and vice versa. The pulling ofthe film 10 by the ridges 24, 26 can stretch the film 10. The rollers12, 14 may not stretch the film 10 evenly along its length.Specifically, the rollers 12, 14 can stretch the portions of the film 10that contact the ridges 24, 26 more than the portions of the film 10that do not contact the ridges 24, 26. Thus, the rollers 12, 14 canimpart or form a striped pattern 36 into the film 10. As used herein,the terms “impart” and “form” refer to the creation of a desiredstructure or geometry in a film upon stretching the film that will atleast partially retain the desired structure or geometry when the filmis no longer subject to any strains or externally applied forces.

As shown in FIGS. 1A and 1B, the striped pattern 36 formed by the MDring rolling process can be visually perceivable. As used herein, theterm “visually perceivable” refers to features that are readilydiscernible to the normal naked eye. In particular, visually perceivablefeatures can be readily discernible to the normal naked eye when a film10 including the features is subjected to normal use.

In one or more implementations, prior to passing through theintermeshing rollers 12, 14, the film 10 may not include a visuallyperceivable striped pattern. For example, FIGS. 1A and 1B illustratethat the pre-stretched film 10 a (i.e., the film that is yet to passthrough the intermeshing rollers 12, 14) can have a substantially flattop surface 38 and substantially flat bottom surface 40. Thepre-stretched film 10 a can have an initial thickness or starting gauge42 extending between its major surfaces (i.e., the top surface 38 andthe bottom surface 40). In at least one implementation, the startinggauge 42 can be substantially uniform along the length of thepre-stretched film 10 a.

For purposes of the present invention, the pre-stretched film 10 a neednot have an entirely flat top surface 38. Indeed, the top surface 38 canbe rough or uneven. Similarly, bottom surface 40 of the pre-stretchedfilm 10 a can also be rough or uneven. Further, the starting gauge 42need not be consistent or uniform throughout the entirety ofpre-stretched film 10 a. Thus, the starting gauge 42 can vary due toproduct design, manufacturing defects, tolerances, or other processingissues.

In any event, FIGS. 1A and 1B illustrate the intermeshing rollers 12, 14can process the pre-stretched film 10 a into an MDincrementally-stretched film 10 b with visually-distinct stretchedregions. As previously mentioned, the MD incrementally-stretched film 10b can include a striped pattern 36. The striped pattern 36 can includealternating series of “un-stretched” regions 44 and stretched regions46. In one or more implementations, the “un-stretched” regions of theincrementally-stretched films may be stretched to a small degree. In anyevent, the “un-stretched” regions are stretched significantly lesscompared to the stretched regions.

The un-stretched regions 44 can have a first average thickness or gauge48. The first average gauge 48 can be approximately equal to thestarting gauge 42. In one or more implementations, the first averagegauge 48 can be less than the starting gauge 42. The stretched regions46 can have a second average thickness or gauge 50. In one or moreimplementations, the second average gauge 50 can be less than both thestarting gauge 42 and the first average gauge 48.

One will appreciate in light of the disclosure herein that the stripedpattern 36 may vary depending on the method used to incrementallystretch the film 10. To the extent that MD ring rolling is used toincrementally stretch the film 10, the striped pattern 36 on the film 10can depend on the pitch 32 of the ridges 24, 26, the DOE 34, and otherfactors. In some implementations, the molecular structure of thethermoplastic material of the film 10 may be rearranged to provide thisshape memory.

FIG. 2 illustrates a top view of the MD incrementally-stretched film 10b with visually-distinct stretched regions. As shown by FIG. 2, thestretched regions 46 can be white and opaque. The localized stretchingof the film 10 in the stretched regions 46 can create voids that providethe stretched regions 46 with whiteness and opacity. In other words, thestretched regions can be stress-whitened. In one or moreimplementations, the stretched regions 46 are non porous, despite thepresence of voids, as previously described herein above.

Additionally, in one or more implementations, despite having a reducedgauge, the stretched regions 46 can be white and opaque. The opacity ofthe stretched regions 46 can result in a pleasing appearance and connotestrength to a consumer. Furthermore, the whiteness and opacity of thestretched regions 46 can signify that the film 10 b has undergone atransformation to modify one or more characteristics of the film 10 b.For example, MD ring rolling the film 10 can increase or otherwisemodify one or more of the tensile strength, tear resistance, impactresistance, or elasticity of the film 10 b. The visually-distinctstretched regions 46 can signify the transformation to a consumer.

Furthermore, the stretched regions 46 can include stripes that extendacross the film 10 b in a direction transverse (i.e., transversedirection) to a direction in which the film was extruded (i.e., machinedirection). As shown by FIG. 2, the stripes or stretched regions 46 canextend across the entire length of the film 10 b. The pitch 32 and theDOE 34 of the ridges 24, 26 of the intermeshing rollers 12, 14 candetermine the width and spacing of the stripes or stretched regions 46.Thus, as explained in greater detail below, by varying the pitch 32and/or DOE 34, the width and/or spacing of the stretched regions 46 canbe varied.

FIG. 2 further illustrates that the stretched regions 46 can beintermittently dispersed about un-stretched regions 44. In particular,each stretched region 46 can reside between adjacent un-stretchedregions 44. Additionally, the stretched regions 46 can be visuallydistinct from the un-stretched regions 44. For example, the stretchedregions 46 can differ from the un-stretched regions 44 in one or more ofcolor or transparency.

Thus, the un-stretched regions 44 can be a color other than white and/ortransparent or translucent. For instance, the un-stretched regions 44can be black, blue, red, another color, or any shade there between.Thus, in one or more implementations, the stretched regions 46 can be alighter shade with increased opacity and the un-stretched regions 44 canbe either (i) white and transparent or translucent, (ii) a color otherthan white and transparent or translucent, or (ii) a color other thanwhite and opaque.

Furthermore, the opacity and color of the visually-distinct stretchedregions 46 can vary based on the degree of stretching. For instance,when the un-stretched regions 44 are red, the stretched regions 46 canbe a lighter shade of red, pink, or even white, along the spectrum ofstretch. When the un-stretched regions 44 are black, the stretchedregions 46 can be a lighter shade of black, grey, and even white,depending on the degree of stretch. Similar to the shade or color, theopacity of the stretched regions 46 can vary based on the degree ofstretching.

As mentioned previously, MD ring rolling is one exemplary method ofincrementally stretching a thermoplastic film to createvisually-distinct stretched regions in accordance with an implementationof the present invention. TD ring rolling is another suitable method ofincrementally stretching a film to create visually-distinct stretchedregions. For example, FIG. 3 illustrates a TD ring rolling process thatincrementally stretches a thermoplastic film 10 by passing the film 10through a pair of TD intermeshing rollers 52, 54. A TD ring rollingprocesses (and associated TD intermeshing rollers 52, 54) can be similarto the MD ring rolling process (and associated MD intermeshing rollers12, 14) described herein above, albeit that the ridges 56, 58 andgrooves 60, 62 of the TD intermeshing rollers 52, 54 can extendgenerally orthogonally to the axes of rotation 16, 20.

Thus, as shown by FIG. 3, as the thermoplastic film 10 passes betweenthe intermeshing rollers 52, 54, the ridges 56, 58 can incrementallystretch the film 10 in the transverse direction. In particular, as thefilm 10 proceeds between the intermeshing rollers 52, 54, the ridges 56,58 can impart or form a striped pattern 36 a into the film 10 to form aTD incrementally-stretched film 10 c with visually-distinct stretchedregions.

FIG. 4 illustrates a view of the TD incrementally-stretched film 10 cwith visually-distinct stretched regions. The striped pattern 36 a caninclude alternating series of un-stretched regions 44 a and stretchedregions 46 a. As shown by FIG. 4, the stretched regions 46 a can bewhite and opaque. The localized stretching of the film 10 in thestretched regions 46 a can create voids that provide the stretchedregions 46 a with whiteness and opacity. In one or more implementations,the stretched regions 46 a are non porous, despite the presence ofvoids, as previously described herein above.

The opacity of the stretched regions 46 a can result in a pleasingappearance and connote strength to a consumer. Furthermore, thewhiteness and opacity of the stretched regions 46 a can signify that thefilm 10 c has undergone a transformation to modify one or morecharacteristics of the film 10 c. For example, TD ring rolling the film10 can increase or otherwise modify one or more of the tensile strength,tear resistance, impact resistance, or elasticity of the film 10 c. Thevisually-distinct stretched regions 46 a can signify the transformationto a consumer.

FIG. 4 illustrates that the stretched regions 46 a can include stripesthat extend across the film 10 c in the machine direction. As shown byFIG. 4, the stripes or stretched regions 46 a can extend across theentire width of the film 10 c. In alternative implementations, stretchedregions 46 a can extend across only a portion of the film 10 c. Similarto MD ring rolling, the pitch and the DOE of the ridges 56, 58 of theintermeshing rollers 52, 54 can determine the width and spacing of thestripes or stretched regions 46 a.

In still further implementations, a film 10 can undergo both an MD ringrolling process and a TD ring rolling process to createvisually-distinct stretched regions. For example, FIG. 5 illustrates atop view of an incrementally-stretched film 10 d with visually-distinctstretched regions created by MD and TD ring rolling. Theincrementally-stretched film 10 d can have a checker board pattern 36 b.The checker board pattern 36 b can include alternating series ofun-stretched regions 44 b and stretched regions 46 b, 46 c. As shown byFIG. 5, stretched regions 46 b, 46 c can be visually distinct from theun-stretched regions 44 b. In particular, stretched regions 46 b, 46 ccan be white and opaque. The stretched regions 46 b, 46 c can includestripes 46 b that extend along the film 10 c in the machine direction,and stripes 46 c that extend along the film in the transverse direction.As shown by FIG. 5, in one or more implementations, the aspect ratio ofthe rows and columns of the stretched regions 46 b, 46 c can beapproximately 1 to 1. In alternative implementations, the aspect ratioof the rows and columns of the rows and columns of the stretched regions46 b, 46 c can be greater or less than 1 to 1, as explained in greaterdetail in relation to FIG. 11.

The incrementally-stretched film 10 d with visually-distinct stretchedregions created by MD and TD ring rolling can allow for even greatermaterial savings by further increasing the surface area of a givenportion of film. Additionally, MD and TD ring rolling can provideproperties or advantages not obtained by MD or TD ring rolling alone.Thus, checker board pattern 36 b created by the stretched regions 46 b,46 c can signify these transformations to a consumer.

In yet further implementations, a manufacturer can use DD ring rollingto incrementally stretch a thermoplastic film to createvisually-distinct stretched regions. A DD ring rolling processes (andassociated DD intermeshing rollers) can be similar to the MD ringrolling process (and associated MD intermeshing rollers 12, 14)described herein above, albeit that the ridges and grooves of the DDintermeshing rollers can extend at an angle relative to the axes ofrotation. For example, FIG. 6 illustrates a view of anincrementally-stretched film 10 e with visually-distinct stretchedregions created by DD ring rolling. The incrementally-stretched film 10e can have a diamond pattern 36 c. The diamond pattern 36 c can includealternating series of diamond-shaped un-stretched regions 44 c andstretched regions 46 d. As shown by FIG. 6, stretched regions 46 d canbe visually distinct. The stretched regions can include stripes 46 doriented at an angle relative to the transverse direction such that thestripes 46 d are neither parallel to the transverse or machinedirection.

One will appreciate in light of the disclosure herein that one or moreimplementations can include stretched regions arranged in otherpatterns/shapes. Such additional patterns include, but are not limitedto, intermeshing circles, squares, diamonds, hexagons, or other polygonsand shapes. Additionally, one or more implementations can includestretched regions arranged in patterns that are combinations of theillustrated and described patterns/shapes.

In accordance with another implementation, a structural elastic likefilm (SELF) process may be used to create a thermoplastic film withstrainable networks. As explained in greater detail below, thestrainable networks can include visually-distinct stretched regions.U.S. Pat. Nos. 5,518,801, 6,139,185; 6,150,647; 6,394,651; 6,394,652;6,513,975; 6,695,476; U.S. Patent Application Publication No.2004/0134923; and U.S. Patent Application Publication No. 2006/0093766each disclose processes to form strainable networks or patterns ofstrainable networks suitable for use with implementations of the presentinvention. The contents of each of the aforementioned patents and patentapplication publications are incorporated in their entirety by referenceherein.

FIG. 7 illustrates a pair of SELF'ing intermeshing rollers 72, 74 forcreating strainable networks with visually-distinct stretched regions ina film. The first SELF'ing intermeshing roller 72 can include aplurality of ridges 76 and grooves 78 extending generally radiallyoutward in a direction orthogonal to an axis of rotation 16. Thus, thefirst SELF'ing intermeshing roller 72 can be similar to a TDintermeshing roller 52, 54. The second SELF'ing intermeshing roller 74can include also include a plurality of ridges 80 and grooves 82extending generally radially outward in a direction orthogonal to anaxis of rotation 20. As shown by FIG. 7; however, the ridges 80 of thesecond SELF'ing intermeshing roller 74 can include a plurality ofnotches 84 that define a plurality of spaced teeth 86.

Referring now to FIG. 8, an incrementally-stretched film 10 f withvisually-distinct stretched regions created using the SELF'ingintermeshing rollers 72, 74 is shown. In particular, as the film passesthrough the SELF'ing intermeshing rollers 72, 74, the teeth 86 can pressa portion of the web out of plane to cause permanent, deformation of aportion of the film in the Z-direction. On the other hand the portionsof the film that pass between the notched regions 84 and the teeth 86will be substantially unformed in the Z-direction, resulting in aplurality of deformed, raised, rib-like elements 88.

As shown by FIG. 8, the strainable network of theincrementally-stretched film 10 f with visually-distinct stretchedregions can include first un-stretched regions 44 d, second un-stretchedregions 44 e, and stretched transitional regions 46 e connecting thefirst and second un-stretched regions 44 d, 44 e. The secondun-stretched regions 44 e and the stretched regions 46 e can form theraised rib-like elements 88 of the strainable network.

FIG. 8 illustrates that the stretched regions 46 e can be visuallydistinct from the un-stretched regions 44 d, 44 e. In particular,stretched regions 46 e can be white and opaque. The stretched regions 46e can be discontinuous or be separated as they extend across the film 10f in both transverse and machine directions. This is in contrast tostripes that extend continuously across a film in one of the machine andtransverse directions.

The rib-like elements 88 can allow the film 10 f to undergo asubstantially “geometric deformation” prior to a “molecular-leveldeformation.” As used herein, the term “molecular-level deformation”refers to deformation which occurs on a molecular level and is notdiscernible to the normal naked eye. That is, even though one may beable to discern the effect of molecular-level deformation, e.g.,elongation of the film, one is not able to discern the deformation whichallows or causes it to happen. This is in contrast to the term“geometric deformation.” As used herein, the term “geometricdeformation” refers to deformations of the film 10 f which are generallydiscernible to the normal naked eye when the film 10 f or articlesembodying the film 10 f are subjected to an applied strain. Types ofgeometric deformation include, but are not limited to bending,unfolding, and rotating.

Thus, upon an applied strain, the rib-like elements 88 can undergogeometric deformation before either the rib-like elements 88 or the flatregions undergo molecular-level deformation. For example, an appliedstrain can pull the rib-like elements 88 back into plane with the flatregions prior to any molecular-level deformation of the film 10 fGeometric deformation can result in significantly less resistive forcesto an applied strain than that exhibited by molecular-level deformation.

Thus, the strainable network of the film 10 f may provide improvedproperties to the film 10 f, such as elasticity, improved tear, andimproved impact properties. The visually-distinct stretched regions 46 ecan provide notice to a consumer that the film 10 f includes theimproved properties provided by the strainable network. Additionally,the opacity of the visually-distinct stretched regions 46 e can providea look or feel of increased thickness and strength.

One will appreciate in light of the disclosure herein that the patternof the strainable network of FIG. 8 is only one pattern suitable for usewith the present invention. For example, FIG. 9 illustrates anotherstrainable network pattern that can include visually-distinct stretchedregions. In particular, FIG. 9 illustrates an incrementally-stretchedfilm 10 g with a strainable network of rib-like elements 88 a arrangedin diamond patterns. The strainable network of theincrementally-stretched film 10 g with visually-distinct stretchedregions can include first un-stretched regions 44 d, second un-stretchedregions 44 e, and stretched transitional regions 46 e connecting thefirst and second un-stretched regions 44 d, 44 e. The stretched regions46 e can be visually distinct from the un-stretched regions 44 d, 44 e.In particular, stretched regions 46 e can be white and opaque.

One or more implementations of the present invention can includestrainable network patterns other than those shown by FIGS. 8 and 9, orcombinations of various patterns. It should be understood that the term“pattern” is intended to include continuous or discontinuous sections ofpatterns, such as may result, for example, from the intersection offirst and second patterns with each other. Furthermore, the patterns canbe aligned in columns and rows aligned in the machine direction, thetransverse direction, or neither the machine or transverse directions.

One will appreciate in light of the disclosure herein that theincrementally-stretched films with visually-distinct stretched regionscan form part of any type of product made from, or incorporating,thermoplastic films. For instance, grocery bags, trash bags, sacks,packaging materials, feminine hygiene products, baby diapers, adultincontinence products, sanitary napkins, bandages, food storage bags,food storage containers, thermal heat wraps, facial masks, wipes, hardsurface cleaners, and many other products can includeincrementally-stretched with visually-distinct stretched regions to oneextent or another. Trash bags and food storage bags may be particularlybenefited by the films of the present invention.

Referring to FIG. 10, in a particular implementation of the presentinvention, the incrementally-stretched film 10 b illustrated in FIG. 2may be incorporated in a bag construction, such as a flexible draw tapebag. The bag 90 can include a bag body 92 formed from a piece ofincrementally-stretched film 10 b folded upon itself along a bag bottom94. Side seams 96 and 98 can bond the sides of the bag body 92 togetherto form a semi-enclosed container having an opening 100 along an upperedge 102. The bag 90 also optionally includes closure means 104 locatedadjacent to the upper edge 102 for sealing the top of the bag 90 to forma fully-enclosed container or vessel. The bag 90 is suitable forcontaining and protecting a wide variety of materials and/or objects.The closure means 104 can comprise flaps, adhesive tapes, a tuck andfold closure, an interlocking closure, a slider closure, a zipperclosure or other closure structures known to those skilled in the artfor closing a bag.

As shown, the sides of the bag body 92 can include un-stretched regions44 and stretched regions 46 in the form of stripes. The stretchedregions 46 can be visually distinct from the un-stretched regions 44. Inparticular, the stretched regions 46 can be white and opaque. Thestripes can extend across the bag 90 in the TD direction, or in otherwords, from the bag bottom 94 to the upper edge 102. The bag 90 canrequire less material to form than an identical bag formed with anun-stretched film 10 a of the same thermoplastic material. Additionally,despite requiring less material, the bag 90 can include improvedproperties imparted by MD ring rolling. The visually-distinct stretchedregions 46 can serve to notify a consumer of the improved properties.Furthermore, while the bag body 92 can include opaque regions created byvoiding agents, the bag body 92 can be non porous. Thus, the bag body 92can prevent liquids, and at least substantially prevent gases, frompassing there through.

FIG. 11 illustrates a tie bag 106 incorporating anincrementally-stretched film with visually-distinct stretched regions inaccordance with an implementation of the present invention. As shown thesides of the tie bag 106 can include a pattern of un-stretched regions44 f and stretched regions 46 f, 46 g created by MD and TD ring rolling.The stretched regions 46 f, 46 g can be visually distinct from theun-stretched regions 44 f. In particular, stretched regions 46 f, 46 gcan be white and opaque.

The visually-distinct stretched regions can include stripes 46 f thatextend across the bag 106 in the machine direction. Additionally,visually-distinct stretched regions can include stripes 46 g that extendacross the bag 106 in the transverse direction, or in other words fromthe bag bottom 108 to flaps 110 of an upper edge 112 of the bag 106.

In comparison with the film 10 d of FIG. 5, the spacing between the MDextending stripes 46 f is greater in the bag 106. This effect is createdby using MD ring rolls having a greater pitch between ridges. Similarly,the spacing of the TD extending stripes 46 g is greater in the bag 106than the film 10 d. This effect is created by using TD ring rolls havinga greater pitch between ridges. Furthermore, the relative spacingbetween the MD extending stripes and the TD extending stripes differs inthe bag 106, while relative spacing is the same in the film 10 d. Thiseffect is created by using TD ring rolls having a greater pitch betweenridges compared to the pitch between ridges of the MD ring rolls. Onewill appreciate in light of the disclosure herein that the use ofintermeshing rollers with greater or varied ridge pitch can provide thedifferent spacing and thicknesses of the stripes. Thus, one willappreciate in light of the disclosure herein that a manufacturer canvary the ridge pitch of the intermeshing rollers to vary the pattern ofthe visually-distinct stretched regions, and thus, the aesthetic and/orproperties of the bag or film.

In addition to the varying the pattern of visually-distinct stretchedregions in a bag or film, one or more implementations also includeproviding visually-distinct stretched regions in certain sections of abag or film, and only un-stretched regions in other sections of the bagor film. For example, FIG. 12 illustrates a bag 114 having an uppersection 116 adjacent a top edge 118 that is devoid of visually-distinctstretched regions. Similarly, the bag 114 includes a bottom section 120adjacent a bottom fold or edge 122 devoid of visually-distinct stretchedregions. In other words, both the top section 116 and bottom section 120of the bag 114 can each comprise un-stretched regions.

A middle section 124 of the bag 114 between the upper and lower sections116, 120 on the other hand can include visually-distinct stretchedregions. In particular, FIG. 12 illustrates that the middle section caninclude a strainable network of rib-like elements arranged in diamondpatterns similar to the film 10 e of FIG. 9. Thus, the middle section124 of the bag 114 can include improved properties, such as elasticityand impact resistance, created by the strainable network. Furthermore,the white and opaque stretched regions (i.e., the stretched transitionalregions of the rib-like elements) can serve to notify a consumer of thatthe middle section 124 includes improved properties.

In one or more additional implementations, the present inventionincludes providing different visually-distinct stretched regions indifferent sections of a bag or film. For example, FIG. 13 illustrates abag 114 a similar to the bag 114 of FIG. 12, albeit that the bottomsection 120 a includes alternating series of un-stretched regions 44 aand stretched regions 46 a created by TD ring rolling. Thus, the middlesection 124 of the bag 114 can include one set of improved propertiescreated by the strainable network, and the bottom section 120 a caninclude another set of improved properties created by TD ring rolling.Furthermore, the white and opaque stretched regions can serve to notifya consumer of the different properties of the middle section 124 and thebottom section 120 a.

FIG. 14 illustrates yet another bag 126 including having an uppersection 116 a adjacent a top edge 118 that includes alternating seriesof un-stretched regions 44 b and visually-distinct stretched regions 46b, 46 c created by MD and TD ring rolling similar to the film 10 d ofFIG. 5. Furthermore, the middle section 124 a of the bag 126 can includeun-stretched regions 44 and stretched regions 46 in the form of stripescreated by MD ring rolling. The stretched regions 46 can be visuallydistinct from the un-stretched regions 44. In particular, stretchedregions 46 can be white and opaque.

Thus, one will appreciate in light of the disclosure herein that amanufacturer can tailor specific sections or zones of a bag or film withdesirable properties by MD, TD, or DD ring rolling, SELF'ing, or acombination thereof. Furthermore, the different visually-distinctstretched regions can serve to notify a consumer of the properties ofthe different sections. One will appreciate in light of the disclosureherein that the visually-distinct stretched regions can be more visuallydiscernable than any geometric deformation alone.

FIG. 15 illustrates an exemplary embodiment of a high-speedmanufacturing process 128 for incrementally stretching a thermoplasticfilm to produce visually-distinct stretched regions and produce aplastic bag there from. According to the process 128, an un-stretchedthermoplastic film 10 including a thermoplastic material and a voidingagent is unwound from a roll 130 and directed along a machine direction.

The un-stretched film 10 can pass between first and second cylindricalintermeshing rollers 134, 136 to incrementally stretch the un-stretchedfilm 10 to create un-stretched regions and visually-distinct stretchedregions in at least one section of the film. The intermeshing rollers134, 136 can have a construction similar to that of intermeshing rollers12, 14 of FIGS. 1A-1B, or any of the other intermeshing rollers shown ordescribed herein. The rollers 134, 136 may be arranged so that theirlongitudinal axes are perpendicular to the machine direction.Additionally, the rollers 134, 136 may rotate about their longitudinalaxes in opposite rotational directions. In various embodiments, motorsmay be provided that power rotation of the rollers 134, 136 in acontrolled manner. As the un-stretched film 10 passes between the firstand second rollers 134, 136, the ridges and/or teeth of the intermeshingrollers 134, 136 can form an incrementally-stretched film 138 withvisually-distinct stretched regions.

During the manufacturing process 128, the incrementally-stretched film138 can also pass through a pair of pinch rollers 140, 142. The pinchrollers 140, 142 can be appropriately arranged to grasp theincrementally-stretched film 138 with visually-distinct stretchedregions. The pinch rollers 140, 142 may facilitate and accommodate theincrementally-stretched film 138 with visually-distinct stretchedregions.

A folding operation 144 can fold the incrementally-stretched film 138with visually-distinct stretched regions to produce the sidewalls of thefinished bag. The folding operation 144 can fold theincrementally-stretched film 138 with visually-distinct stretchedregions in half along the transverse direction. In particular, thefolding operation 144 can move a first edge 148 adjacent to the secondedge 150, thereby creating a folded edge 152. The folding operation 144thereby provides a first film half 154 and an adjacent second web half156. The overall width 158 of the second film half 156 can be half thewidth 158 of the pre-folded incrementally-stretched film 138 withvisually-distinct stretched regions.

To produce the finished bag, the processing equipment may furtherprocess the folded incrementally-stretched film 138 withvisually-distinct stretched regions. In particular, a draw tapeoperation 160 can insert a draw tape 162 into theincrementally-stretched film 138 with visually-distinct stretchedregions. Furthermore, a sealing operation 164 can form the parallel sideedges of the finished bag by forming heat seals 166 between adjacentportions of the folded incrementally-stretched film 138 withvisually-distinct stretched regions. The heat seals 166 may be spacedapart along the folded incrementally-stretched film 138 withvisually-distinct stretched regions. The sealing operation 164 can formthe heat seals 166 using a heating device, such as, a heated knife.

A perforating operation 168 may form a perforation 170 in the heat seals166 using a perforating device, such as, a perforating knife. Theperforations 170 in conjunction with the folded outer edge 152 candefine individual bags 172 that may be separated from theincrementally-stretched film 138. A roll 174 can wind theincrementally-stretched film 138 with visually-distinct stretchedregions embodying the finished bags 172 for packaging and distribution.For example, the roll 174 may be placed into a box or bag for sale to acustomer.

In still further implementations, the folded incrementally-stretchedfilm 138 may be cut into individual bags along the heat seals 166 by acutting operation. In another implementation, the foldedincrementally-stretched film 138 with visually-distinct stretchedregions may be folded one or more times prior to the cutting operation.In yet another implementation, the side sealing operation 164 may becombined with the cutting and/or perforation operations 168.

One will appreciate in light of the disclosure herein that the process128 described in relation to FIG. 15 can be modified to omit or expandedacts, or vary the order of the various acts as desired. For example,FIG. 16 illustrates another manufacturing process 176 for producing aplastic bag having visually-distinct stretched regions imparted therein.The process 176 can be similar to process 128 of FIG. 15, except thatthe un-stretched film 10 is stretched by intermeshing rollers 134, 136after the folding operation 144 has folded the un-stretched film 10 inhalf.

FIG. 17 illustrates yet another manufacturing process 178 for producinga plastic bag having visually-distinct stretched regions impartedtherein. The process 178 can be similar to process 128 of FIG. 15,except that the un-stretched film 10 is folded prior to winding it onthe roll 130 a. Thus, in such implementations, the un-stretched film 10unwound from the roll 130 a is already folded. Additionally, themanufacturing process 178 illustrates that after passing throughintermeshing rollers 134, 136, the film can pass through another set ofintermeshing rollers 180, 182 to impart a second pattern ofvisually-distinct stretched regions to one or more sections of the film.The intermeshing rollers 180, 182 can have a construction similar tothat of intermeshing rollers 52, 54 of FIG. 3, or any of the otherintermeshing rollers shown or described herein.

Implementations of the present invention can also include methods ofincrementally stretching a film of thermoplastic material to producevisually-distinct stretched regions. The following describes at leastone implementation of a method with reference to the components anddiagrams of FIGS. 1A through 17. Of course, as a preliminary matter, oneof ordinary skill in the art will recognize that the methods explainedin detail herein can be modified to install a wide variety ofconfigurations using one or more components of the present invention.For example, various acts of the method described can be omitted orexpanded, and the order of the various acts of the method described canbe altered as desired.

For example, one method in accordance with one or more implementationsof the present invention can include providing a film. For example, themethod can involve providing a film comprising between about 65 andabout 99 percent by weight of a thermoplastic material, and betweenabout 1 and about 35 percent by weight of a voiding agent. Inparticular, the method can involve extruding a film 10 and directing thefilm 10 into a high speed manufacturing system.

The method can also include cold stretching the film 10 incrementally tocreate stretched regions that are white, opaque, and non-porous. In oneor more implementations this can involve imparting a pattern 36 ofun-stretched regions 44 and stretched regions 46 that are visuallydistinct from un-stretched regions 44. For example, the method caninvolve MD ring rolling the film, TD ring rolling the film, DD ringrolling the film, SELF'ing the film, or a combination thereof. Morespecifically, the method can involve passing the film 10 throughintermeshing rollers. As the film 10 passes through the intermeshingrollers, ridges can impart the pattern 36 into the film andincrementally stretch the film 10.

The present invention may be embodied in other specific forms withoutdeparting from its spirit or essential characteristics. The describedembodiments are to be considered in all respects only as illustrativeand not restrictive. The scope of the invention is, therefore, indicatedby the appended claims rather than by the foregoing description. Allchanges that come within the meaning and range of equivalency of theclaims are to be embraced within their scope.

We claim:
 1. A thermoplastic bag, comprising: first and second sidewallsof a thermoplastic film that comprises linear low-density polyethyleneand a voiding agent, the voiding agent being between 5 and 25 percent byweight of the first and second sidewalls, the first and second sidewallsbeing joined along three edges; a plurality of un-stretched regionsformed in one or more of the first sidewall or the second sidewall, theun-stretched regions having a first average thickness; and a pluralityof cold-stretched regions intermittently dispersed about theun-stretched regions, the cold-stretched regions having a second averagethickness that is smaller than the first average thickness; wherein thecold-stretched regions are non-porous and more opaque than theun-stretched regions.
 2. The thermoplastic bag as recited in claim 1,wherein the thermoplastic film comprises between about 65 and about 99percent by weight of a thermoplastic material, and between 5 and 20percent by weight of the voiding agent.
 3. The thermoplastic bag asrecited in claim 1, wherein a color of the cold-stretched regionsdiffers from a color of the un-stretched regions.
 4. The thermoplasticbag as recited in claim 2, wherein the voiding agent comprises calciumcarbonate.
 5. The thermoplastic bag as recited in claim 1, wherein theun-stretched regions are non-porous.
 6. The thermoplastic bag as recitedin claim 1, wherein the cold-stretched regions comprise one or more of:stripes extending along the thermoplastic film in a direction transverseto a direction in which the thermoplastic film was extruded; stripesextending along the thermoplastic film in a direction in which thethermoplastic film was extruded; or discontinuous strainable networksextending in a direction transverse to direction in which thethermoplastic film was extruded.
 7. The thermoplastic bag as recited inclaim 6, wherein the cold-stretched regions comprise: stripes extendingalong the thermoplastic film in a direction in which the thermoplasticfilm was extruded; and stripes extending along the thermoplastic film ina direction transverse to a direction in which the thermoplastic filmwas extruded.
 8. The thermoplastic bag as recited in claim 6, whereinthe cold-stretched regions comprise discontinuous strainable networksarranged in diamond patterns.
 9. The thermoplastic bag as recited inclaim 1, further comprising: a first section, the first plurality ofcold-stretched regions being located entirely in the first section; anda second un-stretched section.
 10. A thermoplastic bag, comprising:first and second sidewalls of a thermoplastic film that comprises avoiding agent, the voiding agent being between 5 and 20 percent byweight of the first and second sidewalls, the first and second sidewallsbeing joined along three edges; a plurality of thick regions formed inone or more of the first sidewall or the second sidewall, the thickregions having a first average thickness; and a plurality ofcold-stretched regions alternating with the thick regions, thecold-stretched regions having a second average thickness that is smallerthan the first average thickness; wherein the cold-stretched regions arenon-porous and more opaque than the thick regions.
 11. The thermoplasticbag as recited in claim 10, wherein the thermoplastic film comprisesbetween about 65 and about 99 percent by weight of a thermoplasticmaterial, and between about 10 and about 15 percent by weight of thevoiding agent.
 12. The thermoplastic bag as recited in claim 11, whereinthe thermoplastic material comprises linear low density polyethylene.13. The thermoplastic bag as recited in claim 11, wherein the voidingagent comprises calcium carbonate.
 14. The thermoplastic bag as recitedin claim 11, wherein the voiding agent comprises between 15 percent byweight of the thermoplastic film.
 15. The thermoplastic bag as recitedin claim 10, wherein a color of the cold-stretched regions differs froma color of the thick regions.
 16. The thermoplastic bag as recited inclaim 10, wherein an average thickness of the cold-stretched regions isless than an average thickness of the thick regions.
 17. Thethermoplastic bag as recited in claim 10, wherein the cold-stretchedregions comprise one or more of: stripes extending along thethermoplastic film in a direction transverse to a direction in which thethermoplastic film was extruded; stripes extending along thethermoplastic film in a direction in which the thermoplastic film wasextruded; or discontinuous strainable networks extending in a directiontransverse to direction in which the thermoplastic film was extruded.18. The thermoplastic bag as recited in claim 17, wherein thecold-stretched regions comprise: stripes extending along thethermoplastic film in a direction in which the thermoplastic film wasextruded; and stripes extending along the thermoplastic film in adirection transverse to a direction in which the thermoplastic film wasextruded.
 19. The thermoplastic bag as recited in claim 10, wherein thecold-stretched regions comprise discontinuous strainable networksarranged in diamond patterns.
 20. The thermoplastic bag as recited inclaim 19, further comprising: a first section, the first plurality ofstretched regions being located entirely in the first section; and asecond thick section.